// #pragma GCC optimize("O3,unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
template <class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define endl '\n';
#define fastio ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define py cout << "YES" << endl;
#define pn cout << "NO" << endl;
#define pb push_back
#define int long long
typedef long double lld;
#define double lld
typedef long long ll;
typedef unsigned long long ull;
const ll inf = 1e18;
const ll mod = 1e9+7;
const int N = 2e5;
vector<int>primes = {2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97};
// Check for queue, priorioty_queue, stack, ordered_set solutions
// stack => LIFO (whatever goes in last comes out last)
// queue => FIFO (whatever goes in first comes out first)
// priority_queue => Dynamic queries of minimum/maximum
// ordered_set => set in vector form
//[order_of_key(k) gives number of elements less than k, while find_by_order(i) gives i^th element]
// To comment multiple lines : ctrl + /
// To find and replace : ctrl+H
void judge(){
srand(time(NULL));
#ifndef ONLINE_JUDGE
freopen("inputB.txt","r",stdin);
freopen("outputB.txt","w",stdout);
freopen("Error.txt", "w", stderr);
#define debug(x...) cerr << #x <<" = "; _print(x); cerr << endl;
#else
#define debug(x...)
#endif
}
void usaco(string s) {
freopen((s + ".in").c_str(),"r",stdin);
freopen((s + ".out").c_str(),"w",stdout);
}
int dijkstra(vector<set<pair<int,ll>>>&adj, vector<int>src){
int n = adj.size();
vector<ll>dist(n,inf);
priority_queue<pair<ll,int>>pq;
for(auto source : src){
dist[source] = 0;
pq.push({0,source});
}
while(!pq.empty()){
auto x = pq.top();
ll d = -1*x.first; int node = x.second;
pq.pop();
if(d!=dist[node]){
continue;
}
for(auto child : adj[node]){
int v = child.first; ll w = child.second;
if((d+w)<dist[v]){
dist[v] = d+w;
pq.push({-1*(d+w),v});
}
}
}
return dist[0]+dist[n-1];
}
void dfs(int node, vector<set<int>>&adj, vector<bool>&vis){
vis[node] = true;
for(auto child : adj[node]){
if(!vis[child]){
dfs(child,adj,vis);
}
}
}
signed main(){
fastio; //judge();
int n,m; cin >> n >> m;
int cost[n][n]; vector<set<int>>adj(n);
for(int i = 0;i<n;i++){
for(int j = 0;j<n;j++){
cost[i][j] = 0;
}
}
vector<vector<int>>type(m);
for(int i = 0,u,v,c,d;i<m;i++){
cin >> u >> v >> c >> d; u--; v--;
type[i] = {d,u,v};
cost[u][v]++;
adj[u].insert(v);
}
sort(type.begin(),type.end());
vector<bool>vis1(n,false),vis2(n,false);
dfs(0,adj,vis1); dfs(n-1,adj,vis2);
if(vis1[n-1] and vis2[0]){
cout << 0; return 0;
}
for(int i = 0;i<m;i++){
int u = type[i][1], v = type[i][2];
fill(vis1.begin(),vis1.end(),false);
fill(vis2.begin(),vis2.end(),false);
if(cost[u][v]==1){
adj[u].erase(adj[u].find(v));
if(cost[v][u]==0){
adj[v].insert(u);
dfs(0,adj,vis1); dfs(n-1,adj,vis2);
if(vis1[n-1] and vis2[0]){
cout << type[i][0]; return 0;
}
adj[v].erase(adj[v].find(u));
}
adj[u].insert(v);
}
else{
if(cost[v][u]==0){
adj[v].insert(u);
dfs(0,adj,vis1); dfs(n-1,adj,vis2);
if(vis1[n-1] and vis2[0]){
cout << type[i][0]; return 0;
}
adj[v].erase(adj[v].find(u));
}
}
}
}
